Even if they end up re-using the first stage in its entirety, they're still throwing away the second stage every single time.
So they're keeping Trigger's broom's handle, maybe giving it a new link of paint and putting new bristles on the business end every time.
This partial re-use may eventually (at least a few decades into the future) come back to bite SpaceX. If someone does ever build something like Skylon, that would significantly change how satellites are designed (smaller submodules) and assembled (in space, not on the ground) to end up being any size the operator wants (bigger is definitely better). And Skylon would be able to do the whole lot very quickly and keep doing it. That's a concept that really allows huge things to be orbited, and requires. Anyone with a glorified firework wouldn't be able to compete.
Anyway, SpaceX have done pretty well to get this far, and now need to focus on launch frequency and reliability. They're still behind the curve on both fronts. Good luck to them. With Ariane 6 coming along they'll need it.